The Million Mask March, with a claimed 450 locations worldwide, is intended to be a peaceful march to protest against a range of issues.
The official group says that the protesters include Anonymous, Occupy, Wikileaks, Oath Keepers, and the Pirate Party.
In Washington D.C. alone, over 17,000 people said on Facebook that they were going to the march, which began at the Washington Monument.
At least dozens of people also appeared in New York City, according to photos.
Photos show hundreds of people out in London and in the Philippines, among other places.
See photos below.
